The head of British MI6 said today that al Qaeda is "rubbing its hands with glee" over former National Security Agency contractor Edward Snowden's release of classified information detailing American and British surveillance programs around the world.

"There is no doubt that the leaks from Edward Snowden are extremely damaging," said Sir John Sawers, who sat alongside the heads of England's MI5 and GCHQ at an unprecedented public parliamentary committee hearing today. "They have put our operations at risk... Al Qaeda are lapping it up."

When a member of Britain's Intelligence and Security Committee, the group questioning the top spies, pressed Sawers to provide specific examples of the damage suffered by British intelligence, Sawers said he could not answer that in public, but offered to address in a closed, private session.

Sawers' comments came after Sir Iain Lobban, head of the GCHQ, Britain's version of the NSA, explained in broad terms the loss of intelligence since the leaks began this summer.

Lobban said there's a danger of a "gradual darkening" of global sources and said surveillance had picked up conversations involving terror targets "in the Middle East, in Afghanistan, in Asia" who discussed how they needed to move to more secure methods of communication in light of the public revelations about the spy programs.

Earlier in the session, the British intelligence chiefs defended the massive surveillance program much in the same way America's top intelligence officials did before U.S. lawmakers months ago -- by stressing the importance of counter-terrorism intelligence to national security and pointing to the allegedly strict legal framework that they say protects citizens.

"Let me put it like this," Lobban said. "If you are a terrorist, a serious criminal, a proliferator, a foreign intelligence target, or if your activities pose a genuine threat to the national or economic security of the United Kingdom, there is a possibility that your communications will be monitored and we will seek to read [them], we will seek to listen to [them]. If you're not, and you're not in contact with one of those people, then you won't be… And that's true, absolutely, whether you're British, you're foreign, wherever you are in the world."

As to why the surveillance capabilities and legal framework were kept hidden from public view, Lobban said some counter-terrorism tactics are "necessarily secret."
However, he said, secret "does not mean sinister."

The session was the first time the public has been given television access to a meeting of Britain's Intelligence and Security Committee.

The hearing was called in response to a flood of media reports about formerly top secret surveillance programs conducted by America's NSA often in close cooperation with the GCHQ.

The reports, written in major newspapers around the world, were based on a massive trove of confidential documents allegedly stolen from the NSA by former NSA contractor Edward Snowden and then handed over to journalists.

Snowden, now living in Russia after being granted temporary asylum, has been charged in the U.S. with espionage-related crimes.

Supporters call him a hero for exposing the NSA's vast foreign and domestic spying programs that included the collection of information on millions of Americans. His critics, including America's top intelligence officials, call him a traitor who compromised national security.